The present invention concerns assemblies for preparing ready to use suspensions or solutions of an active product, such as those described in U.S. Pat. No. 3,917,063.
Such an assembly includes two hermetically closed containers or flasks, one containing an active product generally under the form of a lyophilized dry powder, and the second containing the liquid in which the active product is put in solution or in suspension at the moment of administration. The assembly also has connection means permitting the putting in communication of the two flasks in two steps First the liquid is introduced in the first flask; then the solution or suspension thus formed is aspirated into the second flask.
To that effect, the first flask is generally of glass and is closed by an elastic stopper inserted in its neck and having in its axis a channel covered by a thin, perforable airtight membrane, glued or welded over one side; while the second flask, made of compressible material is closed by a dropper whose extremity has a diameter slightly smaller than that of the preceding channel. In order to allow the assembling and the putting in communication of the two flasks, the mouth of the first flask is surmounted by a socket, which can be internally threaded, or smooth, whereas the second flask possesses a cylindrical threaded part which can be screwed in the socket of the first flask.
Operation of this assembly consists in screwing the second flask in the socket of the first flask in such a manner that the dropper perforates the membrane when it empties into the first flask, thus providing airtightness between the two flasks.
When the second flask is compressed, liquid passes into the first flask; by shaking the assembly, a suspension or solution is formed and on reversing the assembly and relaxing the pressure on the second flask, the solution or suspension is caused to return into the second flask, where it is easy close by placing a stopper on the dropper.
According to one embodiment described in the aforementioned US patent, the base of the threaded socket has an external rim of the same diameter as that of the airtight membrane, and this socket is fixed on the flask by means of a setting metallic ring, resting on the upper side over this rim and on the lower side on the small collar of the first flask Such an assembly has many drawbacks. In the first place, to fix the socket on the first flask requires two distinct pieces, the socket itself, generally of plastic material, and a metallic setting ring. The socket simply resting on top of the rubber stopper demands a delicate centering. The setting of the ring itself represents a separate operation which prevents the setting in series of the different elements of the flask continuously on a single machine. This results in a high cost of production for the pieces and long assembly time.